.contain , body , html{
    margin: 0;
    padding: 0;
    width:100%;
    height: 100%;
}
.topNav{
    width: 100%;
    height: 4%;
    background-color: purple;
}
.mainBox{
    width: 100%;
    height: 160%;
}
.topMask{
    width: 100%;
    height: 20%;
    background-color: aqua;
    position: fixed;
    top: 0;
    left: 0;
    display: none;
}
/*正常整齐的布局*/
/*.products{*/
/*    width: 100%;*/
/*    display: flex;*/
/*    flex-wrap: wrap;*/
/*}*/
/*.products .item{*/
/*    width: 18%;*/
/*    height: 100px;*/
/*    background-color: pink;*/
/*    margin-right: 10px;*/
/*    margin-bottom: 10px;*/
/*}*/
.products{
    width: 100%;
}
.products .box{
    width: 32.5%;
    float: left;
}
.products .middleBox{
    margin: 0 10px 0 10px;
}
.products .item{
    width: 100%;
    margin-bottom: 10px;
}
.products .itemOne{
    height:400px;
    background-color:pink;
}
.products .itemTwo{
    height:620px;
    background-color:green;
}
.products .itemThree{
    height:880px;
    background-color:skyblue;
}